1. Field of the Invention
This invention relates to an improved air vacuum pump having a vent passage therein in order to balance internal pressures generated during the pumping process.
2. Description of the Prior Art
The use of vacuum pumps to create a suction and draw air from a container are known to those of ordinary skill in the art. However, vacuum pumps have a variety of other purposes and applications. The following is a description of different structures and functions for vacuum pumps in common use.
A primary category of vacuum pumps actually used and known to those of ordinary skill in the art are those which operate by means of an eccentric rotor having lamellae or vanes mounted thereon. Typically, the pump housing includes a stator having an internal chamber with a generally cylindrical shape. The eccentrically mounted rotor is furnished with a plurality of lamellae which are pulled outwardly from the rotor by centrifugal force and which form a tight revolving seal against the inside of the cylindrical chamber. Adjacent lamellae form chambers having variable volume depending upon their position with respect to the stator chamber. More specifically, the variable volume chambers are formed between the inner surface of the cylindrical chamber, the outer surface of the rotor and the facing surfaces of adjacent lamellae. In order to obtain suction a port is provided immediately downstream of the area having the minimum radius between the rotor and the cylindrical chamber of the stator body. An exit port is typically placed just upstream of that location. Such vacuum pumps are often referred to as decompressors and are typically employed to pump gases such as air.
Because of their structure, the pumps just described tend to develop large amounts of heat. Much of the heat is produced by the friction of the rotor lamellae against the inner surface of the cylindrical stator chamber. Heat is also generated by the changing volume of the gas as it is compressed in the pump. Therefore, many prior art pumps of this nature are water cooled and have to be very efficiently designed if used for heavily loaded operations or if employed under conditions of stress.
It is also known in the prior art to furnish the stator of an air cooled pump with fins in order to more efficiently dissipate the heat generated by the pump. Unfortunately, air cooling is not an efficient manner of removing heat from heavy pumps which operate for long periods of time. Examples of typical prior art pumps may be found in the Catalog of the inventor. The catalog is entitled "Air Cooled Vacuum Pumps Jurop" and the specific pumps bear model numbers P5M, P35, P3, P5N, P4N, P6N, etc. Accordingly, there exists a great need for efficient and powerful pumps which can operate for long periods of time under heavy stress and which do not require water cooling, or other extraordinary remedies in order to dissipate heat.
Water cooled pumps present special disadvantages when compared to air cooled systems. Specifically they often require a double walling in order to form a jacket for the water cooling liquid. Moreover, special piping may be required to provide cooling liquid to the water jacket and some sort of pumping mechanism is often employed to force the cooling liquid through the water jacket.
It seems evident that if an air cooled vacuum pump could be produced having the desirable cooling characteristics of a water cooled vacuum pump, then the advantages would be most important. For example, because an air cooled pump would not require the complicated piping structure of a water cooled pump, such a pump might be manufactured relatively simply.
Therefore, the purpose and object of the present invention is to provide an efficient air cooled vacuum pump which does not require cooling liquid. Such a pump is relatively simple in structure and accordingly, production costs are minimized. Moreover, the efficiency of the vacuum pump which is the subject of the invention is such that it can function for long periods of time under conditions of high stress without the danger of exhaustion or jamming which frequently occur when water cooled vacuum pumps are employed.